Time delay induction relay with quick reset



May 22, 1962 W. E. GLASS BURN TIME DELAY INDUCTION RELAY WITH QUICK RESET Filed May 26, 1958 Fig.l.

INVENTOR W||l|om E. Glossburn.

BY I @M w United rates Patent 3,036,243 Tilt/IE DELAY INDUCTHQN RELAY WHTH QUXCK RESET William E. Glassburn, Mountainside, NJ, assignor to Westinghouse Electric (Iorporation, East Pittsburgh,

Pa., a corporation of Pennsylvania Fried May 26, 1953, Ser. No. 737,672 6 Claims. (Cl. 317-36) This invention relates to instrument devices and has particular relation to instruments such as relays of the induction type having time-delay characteristics.

The present invention is applicable to instruments of various forms, and will be described in connection with an induction instrument of the type having an electroconductive armature movable under the influence of an electromagnetic driving system. Such induction instruments may include damping means for damping movement of the'armature when the driving system is energized to a predetermined level eflective to move the armature.

Improved control means are provided in the present invention to eliminate the damping when the energization of the driving system falls below the predetermined level. This arrangement enables a desirable quick return of the armature to its initial reset position when the energization of the driving system is reduced below the level eflective to move the armature away from its reset position.

in the present invention, damping means of improved construction is provided to influence the armature with control means effective to permit operation of the damping means in response to movement of the armature away from the reset position towards a spaced controlling position such as a circuit breaker tripping position. The control means is further effective to prevent operation of the damping means in response to movement of the armature toward its reset position resulting from a decrease in the energization of the driving system below the predetermined level.

According to a preferred embodiment of the invention, the armature is in the form of a disc mounted by a shaft for rotation with respect to the driving system. A suitable bias spring is associated with the shaft which biases the disc toward its reset position. The damping means is preferably of the electromagnetic type and is in the form of a pair of relatively movable magnetic field and electroconductive closed loop systems. One of these systems is carried by the moving system of the relay for rotation with the relay disc.

The field system may include a pair of substantially annular non-permanent magnetic pole pieces mounted in spaced concentric relation with each other to define an air gap arcuate about the axis of concentricity. Suitable magnetic flux producing means, preferably in the form of a permanent magnet, is located to establish a magnetic field in the air gap which is substantially uniform throughout a considerable portionv of the air gap. The closed loop system may include a closed loop formed of a plurality of turns of electroconductive wire having a side extending through the air gap parallel to the axis of concentricity.

In a preferred embodiment of the invention, the closed loop is secured to the moving system of the relay for movement with respect to the magnetic field system in response to movement of the armature. The closed loop is conveniently secured to the shaft which supports the disc such that the loop is movable about the axis of the shaft in accordance with movements of the disc. With this arrangement, movement of the loop with respect to the field system results in the establishment of a damping effect upon the disc.

According to the invention, control means are provided to permit operation of the damping system in response 3,fl3h,243 Patented May 22, 19 62 to movement of the disc away from its reset position toward its control position and to prevent operation of the damping system when the disc moves toward its reset position. The control means is preferably in the form of a unidirectional element which is connected in series relation with the electroconductive wire forming the closed loop. The unidirectional element may constitute a conventional diode rectifier and is poled so as to permit the flow of current about the loop when the loop moves through the magnetic field in response to movement of the disc away from its reset position and to prevent the flo-w of cur-rent about the loop as the loop moves through the field when the disc is rotating towards its reset position.

It is, therefore, an object of the invention to provide a time-delay instrument of improved construction.

It is another object of the invention to provide a timedelay instrument having a driving system influencing an armature with an armature damping system including an electroconductive closed loop having a loop side movable with the armature through an air gap provided by a pair of annular spaced concentric pole pieces of a magnetic field system.

It is a further object of the invention to provide a timedelay instrument having a driving system acting upon an armature with damping means influencing the armature and control means for permitting operation of the damping means in response to movement of the armature away from a reset position and preventing operation of the damping system when the armature moves towards its reset position.

It is still another object of the invention to provide a time-delay instrument having a driving system acting upon an armature with damping means influencing the armature including an electroconductive loop mounted for movement with the armature through a magnetic field, and control means for permitting current flow about the loop when the armature moves away from its reset position and preventing current flow about the loop when the armature moves toward its reset position.

it is a still further object of the invention to provide an instrument as defined in the preceding paragraph wherein the control means comprises a diode rectifier connected in series relation with the conductor of the loop.

Other objects of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a schematic representation of an electrical system including an induction relay with parts shown in section and with parts removed; and

FIG. 2 is a view in top 'plan of the relay of FIG. 1 with parts removed. 7

Referring to the drawing, there is illustrated in FIG. 1 an electrical system represented generally by the numeral 1 including an electrical circuit 3. The circuit 3 is iilustrated as including three conductors 5, 7 and 9, and may be either a threephase, alternating-current circuit or a single-phase, three-wire alternating-current circuit. It will be assumed that the circuit 3 is operating at a frequency of 60 cycles per second.

In order to permit interruption and establishment of the circuit 3, there is provided a suitable circuit breaker 11 illustrated as having a trip coil 18 which is effective when energized to operate the breaker 11 for interrupting the circuit 3. The trip coil 13 is to be energized in response to the flow of excessive current in the circuit 3 to operate the breaker 11 for protecting the circuit 3 from damage due to such excessive current.

In order to control energization of the trip coil 13, the present invention provides an instrument in the form of an overcurrent relay device represented generally by the numeral which preferably possesses time-delay characteristics. The relay 15 is illustrated as being of the induction type and includes an electroconductive armature 17, preferably in the form of a disc which is mounted for rotation in any suitable manner by a supporting shaft :19. A spiral spring 21 has an inner end connected to the shaft 19 and an outer end connected to a portion of the stator structure of the relay to bias the shaft 19 and the disc 17 in a clockwise direction, as viewed from the upper end of the shaft 19.

In order to effect movement of the disc 17, there is provided an electromagnetic driving system 23 of any suitable construction. The system 23 is illustrated in FIG. 1 as including a substantially C-shaped magnetic structure 25 preferably formed of a plurality of laminations 27 of any suitable magnetic material. The structure 25 includes an air gap in which a portion of the disc 17 is positioned. A suitable winding 29 surrounds a portion of the structure 25 to establish, when energized, a magnetomotive force which directs magnetic flux through the structure 25, the associated air gap and the portion of the disc 17 in the air gap.

In order to establish a shifting magnetic field in the air gap for effecting rotation of the disc 17 in response to energization of the winding 29, a pair of electroconductive shading coils 3'1 and 33 are positioned to link portions of the magnetic flux traversing the structure 25. The winding 29 is connected for energization from the conductors 5, 7 and 9 by means of current transformers 35, 37' and 39 associated, respectively, with the conductors 5, 7 and 9. When the winding 29 is energized, a shifting magnetic field is established which effects rotation of the disc 17 in a counterclockwise direction, as viewed from the upper end of the shaft 19.

. In order to effect a controlling function, the shaft 19 has secured thereto an operating arm 41 which bears against a suitable adjustable stop 43 under the influence of the spring 21 when the driving system 23 is deenergized. A pair of fixed contacts 45 and 47 are mounted in any suitable manner in spaced relation with each other and wit-h the operating arm 41. The contacts 45 and 47 are located in the path of movement of the arm 41 such that the contact 47 may be moved into engagement with the contact 45 in response to engagement of the arm 41 with the contact 47 or its support. The contact 47 is preferably mounted on a suitable spring support so as to be deflectable towards and away from the contact 45. If desired, the contact 45 may also be carried by a spring support.

The contacts 45 and 47 are connected in series relation in a circuit which includes the trip coil 13 and a suitable source of direct voltage which is represented by the conductors 49. When the contacts 45 and 47 are in engagement produced by predetermined rotation of the disc 17 and the arm 4-1 in response to an overcurrent condition of the circuit 3, the above-mentioned tripping circuit is established which results in energization of the trip coil 13 and operation of the breaker 11 to interrupt the circuit 3.

For various reasons, it is desirable that a substantial delay be provided between the time of energization of the winding 29 by a quantity representing an excessive current in the circuit 3 and the time when the contacts 45 and 47 are moved into engagement. In the present invention, such a time delay is established by the provision of damping means 51. According to the invention, the damping means 51 includes a pair of relatively rotatable magnetic field and electroconductive loop systems.

In the preferred embodiment illustrated, the damping means 51 includes a magnetic field system 53 comprising a pair of annular non-permanent magnetic pole pieces mounted in spaced concentric relation to define an air gap arcuate about the axis of concentricity. As illustrated in FIGS. 1 and 2, an annual inner pole piece 55 is surrounded in spaced relation by an annular outer pole piece 57. The pole pieces 55 and 57 may be formed of any suitable non-magnetic material, such as soft iron.

It is observed with reference to FIGS. 1 and 2 that the pole pieces 55 and 57 are positioned with the axis of concentricity common to the axis of the shaft 19 such that the pole pieces define an air gap 59 which is arcuate about the axis of the shaft 19. The pole pieces 55 and 57 may be secured in position in any suitable manner such as by portions 61 of the stator structure of the relay. Although the pole pieces 55 and 57 are illustrated in FIGS. 1 and 2 as located above the disc 17, they may be located in other positions, if desired. For example, the pole pieces may be positioned beneath the disc rather than above the disc as viewed in FIG. 1.

In order to establish a magnetic field in the air gap 59, the field system includes further a suitable permanent magnet 63 which is illustrated in FIGS. 1 and 2 as positioned in an enlarged portion of the air gap 59 to engage spaced parts of the pole pieces 55 and 57. The magnet 63 may be constructed of any suitable permanent magnetic material and is magnetized with the polarity illustrated in FIGS. 1 and 2 such that the magnetic flux produced by the magnet extends in directions transverse to the axis of the shaft 19. In the embodiment illustrated in FIG. 1, the magnet 63 has north magnetic poles identified by the letter N which are adjacent the outer surface of the inner pole piece 55" and south magnetic poles identified by the letter S which are adjacent the inner surface of the outer pole piece 57. This arrangement is effective to provide a substantially uniform magnetic field throughout the active portion of the air gap 59.

The damping means 51 includes further an electroconductive loop system which is preferably carried by the moving system of the relay for rotation relative to the field system 53 through the magnetic field established thereby. In the embodiment of FIG. 1, there is illustrated an electroconductive closed loop 65 of rectangular configuration formed of a number of turns of electroconductive wire 67, such as copper, to provide a pair of spaced parallel loop sides 69 and 71. The loop is conveniently secured to the shaft 19 in any suitable manner such that one of the loop sides, such as the side 71, extends through the air gap 59 parallel to the shaft 19. With this arrangement, the loop 65 is movable in accordance with movements of the disc 17 through the magnetic field established in the air gap 59.

As best shown in FIG. 2, the loop 65 is positioned at a location corresponding to the reset position of the disc 17 when the winding 29 is deenergized. It is observed that the air gap 59 has a length dimension which is substantially uniform throughout an angle of approximately 270 about the axis of the shaft 19. The magnet 63 is located in a non-uniform portion of the air gap 59, which is spaced from the active uniform portion thereof as clearly shown in FIG. 2. As a result, the magnet 63 is clear of the path of movement of the loop 65.

In order to control operation of the damping means 51, the present invention provides suitable control means efiective to permit operation of the damping means when the disc 17 is moved away from its reset position and to prevent operation of the damping means in response to movement of the disc toward its reset position.

In a preferred embodiment of the invention, the control means is in the form of a unidirectional element 73 which may constitute a conventional diode rectifier. The diode 73 is connected in series relation with the wire 67 of the loop so as to permit current flow about the loop when the disc 17 moves away from the reset position and to prevent such current flow when the disc is rotating towards its reset position. In the embodiment illustrated in FIG. 2, the diode 73 is supported by the loop 65 at the upper end of the loop. The diode may be secured to the loop in any suitable manner.

With the arrangement illustrated, movement of the loop 65 in a counterclockwise direction as viewed in FIG. 2 will result in the induction of a voltage in the Wire 65 of the loop which directs current along the upper end of the loop in the direction represented by the arrow 75 of FIG. 2. The diode 73 is so poled as to permit such current flow with the result that the desired damping action is obtained. When the loop is moved in a clockwise direction as viewed in FIG. 2 in response to rotation of the disc 17 toward its reset position, a voltage is induced in the Wire of the loop which tends to cause current to flow along the upper end of the loop in the direction opposite to that indicated by the arrow 75. This current flow, however, is prevented due to the characteristic of the diode 73. As a result, no damping action is realized and the disc 17 is free to quickly rotate to its reset position under the influence of the spring 21.

Although the invention has been described with reference to certain specific embodiments thereof, numerous modifications are possible and it is desired to cover only modifications falling within the spirit and scope of the invention.

I claim as my invention:

1. In a time-delay instrument, driving means, armature means mounted for movement relative to said driving means under the influence of the driving means, said armature means being movable between spaced reset and control positions, biasing means for biasing the armature means toward the reset position, said driving means being eifective when energized in accordance with an energizing quantity in excess of a preselected amount to move said armature means away from said reset position towards said control position, electromagnetic damping means including energizable conductor means, said damping means being effective in response to energization of said conductor means for damping movement of said armature means towards said control position, and an asymmetric current flow control device for controlling current flow through said conductor means, said control device being arranged to permit current flow in said conductor means in response to movement of said armature means away from said reset position towards said control position, and to restrict current flow in said conductor means in response to movement of said armature means away from said control position towards said reset position.

2. In a time-delay instrument, driving means, armature means mounted for movement about an axis relative to said driving means under the influence of the driving means, said armature means being movable between spaced reset and control positions, biasing means for biasing the armature means towards the reset position, said driving means being effective when energized in accordance with an energizing quantity in excess of a preselected amount to move said armature mean-s away from said reset position towards said control position, electromagnetic damping means, said damping means including a magnetic field producing device and an electroconductive loop device linking the magnetic field produced by said field device, one of said devices being mounted for movement with said armature means relative to the other of said devices, and means controlling current flow through said loop device and effective to provide a greater degree of energization of said loop device upon relative movement of said devices in a first direction than upon relative movement in the opposite direction.

3. In a time-delay instrument, driving means, armature means mounted for movement relative to said driving means under the influence of the driving means, said armature means being movable in two directions between spaced reset and control positions, biasing means for biasing the armature means towards the reset position, said driving means being effective when energized in accordance with an energizing quantity in excess of a preselected amount to move said armature means away from said reset position towards said control position, electromagnetic damping means effective when energized for damping movement of said armature means, said damping means including a constantly energized magnetic field producing device, and an electroconductive loop device linking the magnetic field produced by said field device, one of said devices being mounted for movement with said armature means relative to the other of said devices, and current flow control means for controlling current flow through said loop for regulating the operation of said damping means, said control means being arranged to permit current flow through said loop in response to movement of said armature in one of said directions, and to prevent current flow through said loop in response to movement of said armature in a second of said directions.

4. In a time-delay instrument, driving means, armature means mounted for movement in two directions relative to said driving means under the influence of the driving means, said armature means being movable between spaced reset and control positions, biasing means for biasing the armature means towards the reset position, said driving means being effective when energized in accordance with an energizing quantity in excess of a preselected amount to move said armature means away from said reset position towards said control position, electromagnetic damping means effective when energized for damping movement of said armature means towards said control position, said damping means including a magnetic field producing device, and an electroconductive loop device linking the magnetic field produced by said field device, one of said devices being mounted for movement with said armature means relative to the other of said devices, and control means for controlling operation of said damping means, said control means comprising a unidirectional element connected in series relation with the conductor of said loop, said element being poled to permit current flow about the loop resulting from movement of said armature means in one of said directions, and to prevent current flow about the loop resulting from movement of said armature means in a second of said directions.

5. In an induction instrument, electromagnetic driving means, electroconductive armature means mounted for movement relative to said driving means under the influence of the driving means, said armature means being movable between spaced reset and control positions, biasing means for biasing the armature means towards the reset position, said driving means being effective when energized in accordance with an electrical quantity in excess of a preselected amount to move said armature means away from said reset position towards said control position, electromagnetic damping means effective when energized for damping movement of said armature means towards said control position, said damping means including a magnetic field producing device, and an electroconductive loop device linking the magnetic field produced by said field device, said loop device being mounted for rotation with said armature means relative to said field device, and control means for controlling operation of said damping means, said control means comprising a unidirectional element connected in series relation with the conductor of said loop, said element being poled to permit current flow about the loop resulting from movement of said armature means towards said control position, and to prevent current flow about the loop resulting from movement of said armature means towards said reset position.

6. In an induction instrument, electromagnetic driving means, electroconductive armature means mounted for movement relative to said driving means under the infiuence of the driving means, said armature means being movable between spaced reset and control positions, biasing means for biasing the armature means towards the reset position, said driving means being efiective when energized in accordance with an electrical quantity in excess of a preselected amount to move said armature means away from said reset position towards said control position, electromagnetic damping. means efiective when energized tor damping movement of said armature means towards said control position, said damping means including a pair of substantially annular pole pieces mounted in spaced concentric relation to define an air gap arcuate about the axis of rotation of said armature means, a permanent magnet positioned to establish a magnetic field in the air gap extending radially of said axis, and an electroconductive loop mounted with a loop side extending parallel to said axis through the air gap for rotation with the armature means about the axis relative to the pole pieces, and control means for controlling operation of said damping means, said control means comprising a unidirectional element connected in series relation with the conductor of said loop, said element being poled to permit current flow about the loop resulting from movement of said armature means towards said control position, and to prevent current flow about the loop resulting from movement of said armature means towards said reset position.

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